A veset can be based on a specific and unique physical symptom that foretells the onset of menstruation. This is called a a veset haguf. It is necessary to take note of the premenstrual symptom, marking when it started and when menstruation began. The following month the veset haguf should be observed: if the premenstrual symptom recurs, the couple must abstain from relations on the onah when the period is expected, and the woman must do a bedikah before they resume relations.

If three times in a row you have had the same symptom (i.e. either a headache OR back pain) a set interval before the arrival of your period, meaning you know specifically which day and onah your period will arrive, then you have a veset kavua and no longer need to observe the regular three onot, However, if you get your period sometimes without this symptom preceding it, OR if the onset of your period is not always a set interval after your symptom, then you must observe the veset haguf of the previous cycle as well as the regular three onot – yom hachodesh, yom hahaflagah, and onah beinonit.

In any case, if you feel you period is imminent, you should abstain from marital relations.

Since the details here are important, and the halachot are complex, we encourage you to contact a halachic authority or our hotline for more comprehensive guidelines.

Updated 8 August, 2023.